<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		
		<script type="text/javascript">
			var a = "1";
			console.log(a == true);//a和true都转换成数字再比较
			
			/**
			 * undefined是null的衍生值，所以 undefined == null
			 * */
			var b = undefined;
			var c = null;
			console.log(b == c);
			
			/**
			 * NaN不和任何值相等，包括它本身
			 * */
			b = NaN;
			c = NaN;
			console.log(b == c);
			/**
			 * 可以通过isNan()函数来判断值是否是NaN
			 * */
			 console.log(isNaN(b));
		</script>
	</body>
</html>
